diff --git a/du3/README.md b/du3/README.md
new file mode 100644
index 0000000..fb5ab1f
--- /dev/null
+++ b/du3/README.md
@@ -0,0 +1 @@
+Na túto úlohu som použil copilot a Claude Haiku 4.5, aby som si ujasnil, čo je 'parse' a ako ho používať. Použil som ho aj na preklad úlohy.
\ No newline at end of file
diff --git a/du3/program.c b/du3/program.c
new file mode 100644
index 0000000..7ff70c3
--- /dev/null
+++ b/du3/program.c
@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <ctype.h>
+
+int main() {
+
+    char line[256];
+
+    while (fgets(line, sizeof(line), stdin) != NULL) {
+      //nothing
+        line[strcspn(line, "\n")] = 0;
+//empty line
+
+        if (strlen(line) == 0) {
+            break;
+        }
+
+      //nospace
+        char pusto[256];
+        int j = 0;
+        for (int i = 0; line[i] != '\0'; i++) {
+            if (!isspace(line[i]) ) {
+
+                pusto[j = j + 1] = line[i];
+            }
+        }
+        pusto[j] = '\0';
+
+        // Parse
+        double n1;
+        double n2;
+        double expect;
+        char op;
+        int parsed = sscanf(pusto, "%lf%c%lf=%lf", &n1, &op, &n2, &expect);
+
+        if (parsed != 4) {
+            printf("CHYBA\n");
+            continue;
+        }
+// is valid
+        if (op != '+' && op != '-' && op != '*' && op != '/') {
+            printf("CHYBA\n");
+            continue;
+        }
+
+       // resultat
+        double teraz;
+        switch (op) {
+            case '+':
+                teraz = n1 + n2;
+                break;
+            case '-':
+                teraz = n1 - n2;
+                break;
+            case '*':
+                teraz = n1 * n2;
+                break;
+            case '/':
+                if (n2 == 0.0) {
+                    printf("CHYBA\n");
+                    continue;
+                }
+                teraz = n1 / n2;
+                break;
+        }
+
+        // zaokrouhleni
+        double rounded_teraz = round(teraz * 100.0) / 100.0;
+        double rounded_expect = round(expect * 100.0) / 100.0;
+
+        if (fabs(rounded_teraz - rounded_expect) < 1e-9) {
+            printf("OK\n");
+        } else {
+            printf("ZLE\n");
+        }
+    }
+    return 0;
+}